The invention resides in the mechanical field and can advantageously be used in medical engineering. It relates to a sheath device for inserting a catheter into a patient's body, wherein the sheath leads into the patient's body and a proximal end of the sheath protrudes therefrom. The sheath provides a lumen, through which a catheter can be inserted into the patient's body.
Such sheath devices are known in principle. They are used to insert various catheters, for example in the minimally invasive medical field. Such a sheath can, for example, be provided for inserting a blood pump for cardiac support, such a unit comprising a distal pump unit, a hollow catheter and a drive shaft which is guided through the hollow catheter. In miniaturized form, such pumps are often times designed so that they can be radially compressed and inserted, in the compressed state, together with the catheter through a blood vessel of the body. The pump can then be expanded at the site of use, for example in a blood vessel or in a ventricle. In the expanded state, with delivery elements activated, such a pump can then attain the required pumping capacity.
In addition to such compressible heart pumps, other functional elements are also conceivable, which are introduced into a cavity of a body by means of a sheath according to the invention, such as stents or milling heads for removing plaque from vessels.
Compared to a direct insertion, inserting such functional elements and catheters by means of a sheath is considerably easier and also associated with fewer medical risks.
The sheath itself can be inserted, for example into a vascular system, using the known Seldinger Technique. For this purpose, first an opening is introduced in a body vessel by means of a puncturing needle, whereupon a guide wire is pushed in. A dilator is then optionally introduced via the guide wire, and thereupon the sheath itself is pushed in. The guide wire can then be removed, unless it is required for further guide tasks, and other elements can be introduced via the sheath.
A corresponding method is known from WO 02/43791, for example. According to this document, a heart pump is advanced along a guide wire into the left ventricle of a patient and a pump unit is advanced out of the sheath through the vascular system to the ventricle.
A corresponding fluid pump, which is provided for high rotational speeds so as to achieve a corresponding pumping capacity, in the form of a blood pump is likewise known from WO 02/43791 A1, but also from EP 2 047 872. EP 2 047 872 A1 describes a pump which comprises a distal pump unit, to which a proximal shaft hollow catheter adjoins. A drive shaft extending in the shaft catheter is connected to a drive unit for driving the rotor of the pump.
Using a convenient sheath for inserting a catheter, notably comprising a drive shaft, has the advantage that the catheter, and more particularly a drive shaft, experiences less mechanical stress during insertion. This is advantageous in particular with high mechanical stresses to which a drive shaft is exposed when a blood pump is operated.
For a convenient use of a corresponding sheath for inserting a catheter, notably comprising a distal pump unit, it is desirable to be able to advance the sheath, together with the hollow catheter, as close as possible to the vicinity of the site of use and then remove the shaft catheter or the pump from the sheath, so as to then be able to retract the sheath at least a certain distance. The unit to be introduced is thus moved the shortest possible distance in the vascular system or corresponding cavities of the patient's body outside a sheath, so that the strain on the vascular walls due to insertion of the foreign object as well as the mechanical stress of the unit to be inserted are substantially reduced.
On the other hand, such a procedure requires a corresponding excess length of the sheath, which after being advanced and subsequently retracted typically protrudes a certain distance from the patient's body.